tiling a sealed gypsum screed??? Advice needed - TilersForums.com

[davy_G]

Hi all,
I was looking at a friends not so new, new build this evening.

He wants a decent amount of tiling done. The main job is on a sealed gypsum screed.
The screed was put in and polished about a year ago. It is over a wet UFH system.

They where advised to seal the screed with an water based arcylic sealer, this was done.

It looks very much like a garage floor paint, with not much info on the used tin.

I intended to get the UFH turned down to +/-10C. Prime with SBR (this is the bit i have the problem with!) and tile with flexi addy & grout.

The problem i have is the floor is highly polished and the sealer is quite glossy. and the worrying bit. Another chap, whos work they are not happy with, did the bathroom and the floor tiles have started to debond. The tiler supplied the adhesive and grout so i have no idea as to its suitability.
I hava asked my mate to lift some of the tiles as he is going to attempt a remair job and see where it has debonded, if its clean from the sealer and all the adhesive is on the tile that will worry me, if it pants adhesive then im happy enough to proceed.

I have an option to acid etch the sealer/paint, then prime. Whats your toughts? There is no point me putting down tiles for them to potentially lift, i dont want a call in 6 months time.

 

[Ian]

Was the screed sanded before it was sealed?

 

[jay]

Think you need to grind or sand the sealer off first so your adh can get a key

 

[Gazzer]

Ajax is the man for this . I would think that sanding the floor would be a start. Why not use a Gypsum adhesive ?

 

[davy_G]

Was the screed sanded before it was sealed?

As in polished?
Yes

 

[Ian]

I mean sanded to remove any laitence? Either way I think you need to do it again to get rid of the primer/sealer as Jay has suggested and from experience, use a gypsum based adhesive as Neale has suggested. Ajax has mentioned before that he is yet to see a failure where gypsum based adhesive has been used but, has seen a few where cement based has.

 

[davy_G]

This is my first gypsum screed ive seen, so bear with me.

Ive only used or seen cement adhesive, who manufactures a gypsum one and have you any idea of cost for one suitable for UFH?

 

[Gazzer]

Just used Nicobond Gypfix, good stuff. Price depends on where you buy it from.

 

[hillhead]

Ask your bro Davy if his company does a gypsum adhesive, i personally have never used one myself.
Two weeks ago i was on a sweet marble job and the company had another tiler starting a house close to where i was, the tiler sanded the floors and scratched them for two days. He then primed and left for a week still unsure if he was going to tile it,lol.

 

[Ian]

The one I've used is Creative Impressions with their own primer, a few of the guys on here have used the N&C gear and that goes on with no primer (screed still needs to be sanded and hoovered) from memory the CI is £32 for a 25k bag, don't know about the N&C but i think it's much cheaper.